Gotcha, I've never seen one setup like that for sale, But, there is a simple fitting you can get that does exactly that. They have it at ace for sure, not so sure if the big stores have it. I'm going to ace soon, I can post the name shortly, it's basically a sliding PVC connector, you could prob just put that piece in line below the T of the durso. They used that fitting on the older models of Bermuda aquatics skimmers before they put the gate valve in.
Edit- this is what I'm referring to, is this what u r looking for?
Telescoping couple
http://flexpvc.com/cart/agora.cgi?product=PVC-Couples-Telescoping